Auto merge of #137143 - matthiaskrgr:rollup-9hapmyd, r=matthiaskrgr

Rollup of 8 pull requests

Successful merges:

 - #136986 (Apply unsafe_op_in_unsafe_fn to the standard library)
 - #137012 (add docs and ut for bootstrap util cc-detect)
 - #137072 (Load all builtin targets at once instead of one by one in check-cfg)
 - #137102 (Rework `name_regions` to not rely on reverse scc graph for non-member-constrain usages)
 - #137112 (Don't project into `NonNull` when dropping a `Box`)
 - #137114 (Add an example for `std::error::Error`)
 - #137117 (Fix test that relies on error language)
 - #137119 (fix broken `x {doc, build} core`)

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -14,7 +14,10 @@ use rustc_infer::infer::{NllRegionVariableOrigin, RelateParamBound};
 use rustc_middle::bug;
 use rustc_middle::hir::place::PlaceBase;
 use rustc_middle::mir::{AnnotationSource, ConstraintCategory, ReturnConstraint};
-use rustc_middle::ty::{self, GenericArgs, Region, RegionVid, Ty, TyCtxt, TypeVisitor};
+use rustc_middle::ty::fold::fold_regions;
+use rustc_middle::ty::{
+    self, GenericArgs, Region, RegionVid, Ty, TyCtxt, TypeFoldable, TypeVisitor,
+};
 use rustc_span::{Ident, Span, kw};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::error_reporting::infer::nice_region_error::{
@@ -183,6 +186,17 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         }
     }
 
+    /// Map the regions in the type to named regions, where possible.
+    fn name_regions<T>(&self, tcx: TyCtxt<'tcx>, ty: T) -> T
+    where
+        T: TypeFoldable<TyCtxt<'tcx>>,
+    {
+        fold_regions(tcx, ty, |region, _| match *region {
+            ty::ReVar(vid) => self.to_error_region(vid).unwrap_or(region),
+            _ => region,
+        })
+    }
+
     /// Returns `true` if a closure is inferred to be an `FnMut` closure.
     fn is_closure_fn_mut(&self, fr: RegionVid) -> bool {
         if let Some(ty::ReLateParam(late_param)) = self.to_error_region(fr).as_deref()
@@ -314,7 +328,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                     let type_test_span = type_test.span;
 
                     if let Some(lower_bound_region) = lower_bound_region {
-                        let generic_ty = self.regioncx.name_regions(
+                        let generic_ty = self.name_regions(
                             self.infcx.tcx,
                             type_test.generic_kind.to_ty(self.infcx.tcx),
                         );
@@ -323,7 +337,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                             self.body.source.def_id().expect_local(),
                             type_test_span,
                             Some(origin),
-                            self.regioncx.name_regions(self.infcx.tcx, type_test.generic_kind),
+                            self.name_regions(self.infcx.tcx, type_test.generic_kind),
                             lower_bound_region,
                         ));
                     } else {
@@ -354,9 +368,13 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 }
 
                 RegionErrorKind::UnexpectedHiddenRegion { span, hidden_ty, key, member_region } => {
-                    let named_ty = self.regioncx.name_regions(self.infcx.tcx, hidden_ty);
-                    let named_key = self.regioncx.name_regions(self.infcx.tcx, key);
-                    let named_region = self.regioncx.name_regions(self.infcx.tcx, member_region);
+                    let named_ty =
+                        self.regioncx.name_regions_for_member_constraint(self.infcx.tcx, hidden_ty);
+                    let named_key =
+                        self.regioncx.name_regions_for_member_constraint(self.infcx.tcx, key);
+                    let named_region = self
+                        .regioncx
+                        .name_regions_for_member_constraint(self.infcx.tcx, member_region);
                     let diag = unexpected_hidden_region_diagnostic(
                         self.infcx,
                         self.mir_def_id(),

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -204,7 +204,13 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// that the regions produced are in fact equal to the named region they are
     /// replaced with. This is fine because this function is only to improve the
     /// region names in error messages.
-    pub(crate) fn name_regions<T>(&self, tcx: TyCtxt<'tcx>, ty: T) -> T
+    ///
+    /// This differs from `MirBorrowckCtxt::name_regions` since it is particularly
+    /// lax with mapping region vids that are *shorter* than a universal region to
+    /// that universal region. This is useful for member region constraints since
+    /// we want to suggest a universal region name to capture even if it's technically
+    /// not equal to the error region.
+    pub(crate) fn name_regions_for_member_constraint<T>(&self, tcx: TyCtxt<'tcx>, ty: T) -> T
     where
         T: TypeFoldable<TyCtxt<'tcx>>,
     {

compiler/rustc_middle/src/mir/tcx.rs

@@ -86,6 +86,14 @@ impl<'tcx> PlaceTy<'tcx> {
         }
     }
 
+    pub fn multi_projection_ty(
+        self,
+        tcx: TyCtxt<'tcx>,
+        elems: &[PlaceElem<'tcx>],
+    ) -> PlaceTy<'tcx> {
+        elems.iter().fold(self, |place_ty, &elem| place_ty.projection_ty(tcx, elem))
+    }
+
     /// Convenience wrapper around `projection_ty_core` for
     /// `PlaceElem`, where we can just use the `Ty` that is already
     /// stored inline on field projection elems.
@@ -167,11 +175,7 @@ impl<'tcx> Place<'tcx> {
     where
         D: HasLocalDecls<'tcx>,
     {
-        projection
-            .iter()
-            .fold(PlaceTy::from_ty(local_decls.local_decls()[local].ty), |place_ty, &elem| {
-                place_ty.projection_ty(tcx, elem)
-            })
+        PlaceTy::from_ty(local_decls.local_decls()[local].ty).multi_projection_ty(tcx, projection)
     }
 
     pub fn ty<D: ?Sized>(&self, local_decls: &D, tcx: TyCtxt<'tcx>) -> PlaceTy<'tcx>

compiler/rustc_mir_transform/src/elaborate_drop.rs

@@ -89,6 +89,7 @@ pub(crate) trait DropElaborator<'a, 'tcx>: fmt::Debug {
 
     // Accessors
 
+    fn patch_ref(&self) -> &MirPatch<'tcx>;
     fn patch(&mut self) -> &mut MirPatch<'tcx>;
     fn body(&self) -> &'a Body<'tcx>;
     fn tcx(&self) -> TyCtxt<'tcx>;
@@ -180,7 +181,14 @@ where
 {
     #[instrument(level = "trace", skip(self), ret)]
     fn place_ty(&self, place: Place<'tcx>) -> Ty<'tcx> {
-        place.ty(self.elaborator.body(), self.tcx()).ty
+        if place.local < self.elaborator.body().local_decls.next_index() {
+            place.ty(self.elaborator.body(), self.tcx()).ty
+        } else {
+            // We don't have a slice with all the locals, since some are in the patch.
+            tcx::PlaceTy::from_ty(self.elaborator.patch_ref().local_ty(place.local))
+                .multi_projection_ty(self.elaborator.tcx(), place.projection)
+                .ty
+        }
     }
 
     fn tcx(&self) -> TyCtxt<'tcx> {
@@ -410,12 +418,26 @@ where
 
         let unique_place = self.tcx().mk_place_field(self.place, FieldIdx::ZERO, unique_ty);
         let nonnull_place = self.tcx().mk_place_field(unique_place, FieldIdx::ZERO, nonnull_ty);
-        let ptr_place = self.tcx().mk_place_field(nonnull_place, FieldIdx::ZERO, ptr_ty);
-        let interior = self.tcx().mk_place_deref(ptr_place);
 
+        let ptr_local = self.new_temp(ptr_ty);
+
+        let interior = self.tcx().mk_place_deref(Place::from(ptr_local));
         let interior_path = self.elaborator.deref_subpath(self.path);
 
-        self.drop_subpath(interior, interior_path, succ, unwind)
+        let do_drop_bb = self.drop_subpath(interior, interior_path, succ, unwind);
+
+        let setup_bbd = BasicBlockData {
+            statements: vec![self.assign(
+                Place::from(ptr_local),
+                Rvalue::Cast(CastKind::Transmute, Operand::Copy(nonnull_place), ptr_ty),
+            )],
+            terminator: Some(Terminator {
+                kind: TerminatorKind::Goto { target: do_drop_bb },
+                source_info: self.source_info,
+            }),
+            is_cleanup: unwind.is_cleanup(),
+        };
+        self.elaborator.patch().new_block(setup_bbd)
     }
 
     #[instrument(level = "debug", ret)]

compiler/rustc_mir_transform/src/elaborate_drops.rs

@@ -138,6 +138,10 @@ impl InitializationData<'_, '_> {
 impl<'a, 'tcx> DropElaborator<'a, 'tcx> for ElaborateDropsCtxt<'a, 'tcx> {
     type Path = MovePathIndex;
 
+    fn patch_ref(&self) -> &MirPatch<'tcx> {
+        &self.patch
+    }
+
     fn patch(&mut self) -> &mut MirPatch<'tcx> {
         &mut self.patch
     }

compiler/rustc_mir_transform/src/patch.rs

@@ -166,6 +166,14 @@ impl<'tcx> MirPatch<'tcx> {
         Local::new(index)
     }
 
+    /// Returns the type of a local that's newly-added in the patch.
+    pub(crate) fn local_ty(&self, local: Local) -> Ty<'tcx> {
+        let local = local.as_usize();
+        assert!(local < self.next_local);
+        let new_local_idx = self.new_locals.len() - (self.next_local - local);
+        self.new_locals[new_local_idx].ty
+    }
+
     pub(crate) fn new_block(&mut self, data: BasicBlockData<'tcx>) -> BasicBlock {
         let block = BasicBlock::new(self.patch_map.len());
         debug!("MirPatch: new_block: {:?}: {:?}", block, data);

compiler/rustc_mir_transform/src/shim.rs

@@ -350,6 +350,9 @@ impl fmt::Debug for DropShimElaborator<'_, '_> {
 impl<'a, 'tcx> DropElaborator<'a, 'tcx> for DropShimElaborator<'a, 'tcx> {
     type Path = ();
 
+    fn patch_ref(&self) -> &MirPatch<'tcx> {
+        &self.patch
+    }
     fn patch(&mut self) -> &mut MirPatch<'tcx> {
         &mut self.patch
     }

compiler/rustc_session/src/config/cfg.rs

@@ -29,7 +29,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
 use rustc_lint_defs::BuiltinLintDiag;
 use rustc_lint_defs::builtin::EXPLICIT_BUILTIN_CFGS_IN_FLAGS;
 use rustc_span::{Symbol, sym};
-use rustc_target::spec::{PanicStrategy, RelocModel, SanitizerSet, TARGETS, Target, TargetTuple};
+use rustc_target::spec::{PanicStrategy, RelocModel, SanitizerSet, Target};
 
 use crate::Session;
 use crate::config::{CrateType, FmtDebug};
@@ -432,11 +432,7 @@ impl CheckCfg {
                     panic!("unable to get all the check-cfg values buckets");
                 };
 
-                for target in TARGETS
-                    .iter()
-                    .map(|target| Target::expect_builtin(&TargetTuple::from_tuple(target)))
-                    .chain(iter::once(current_target.clone()))
-                {
+                for target in Target::builtins().chain(iter::once(current_target.clone())) {
                     values_target_abi.insert(Symbol::intern(&target.options.abi));
                     values_target_arch.insert(Symbol::intern(&target.arch));
                     values_target_endian.insert(Symbol::intern(target.options.endian.as_str()));

compiler/rustc_target/src/spec/mod.rs

@@ -1658,6 +1658,14 @@ macro_rules! supported_targets {
             Some(t)
         }
 
+        fn load_all_builtins() -> impl Iterator<Item = Target> {
+            [
+                $( targets::$module::target, )+
+            ]
+            .into_iter()
+            .map(|f| f())
+        }
+
         #[cfg(test)]
         mod tests {
             // Cannot put this into a separate file without duplication, make an exception.
@@ -3360,6 +3368,11 @@ impl Target {
         }
     }
 
+    /// Load all built-in targets
+    pub fn builtins() -> impl Iterator<Item = Target> {
+        load_all_builtins()
+    }
+
     /// Search for a JSON file specifying the given target tuple.
     ///
     /// If none is found in `$RUST_TARGET_PATH`, look for a file called `target.json` inside the

library/core/src/alloc/global.rs

@@ -70,7 +70,7 @@ use crate::{cmp, ptr};
 ///         {
 ///             return null_mut();
 ///         };
-///         self.arena.get().cast::<u8>().add(allocated)
+///         unsafe { self.arena.get().cast::<u8>().add(allocated) }
 ///     }
 ///     unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {}
 /// }

library/core/src/error.rs

@@ -22,6 +22,30 @@ use crate::fmt::{self, Debug, Display, Formatter};
 /// accessing that error via [`Error::source()`]. This makes it possible for the
 /// high-level module to provide its own errors while also revealing some of the
 /// implementation for debugging.
+///
+/// # Example
+///
+/// Implementing the `Error` trait only requires that `Debug` and `Display` are implemented too.
+///
+/// ```
+/// use std::error::Error;
+/// use std::fmt;
+/// use std::path::PathBuf;
+///
+/// #[derive(Debug)]
+/// struct ReadConfigError {
+///     path: PathBuf
+/// }
+///
+/// impl fmt::Display for ReadConfigError {
+///     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+///         let path = self.path.display();
+///         write!(f, "unable to read configuration at {path}")
+///     }
+/// }
+///
+/// impl Error for ReadConfigError {}
+/// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 #[cfg_attr(not(test), rustc_diagnostic_item = "Error")]
 #[rustc_has_incoherent_inherent_impls]

library/core/src/hint.rs

@@ -52,7 +52,7 @@ use crate::{intrinsics, ub_checks};
 ///             // Safety: `divisor` can't be zero because of `prepare_inputs`,
 ///             // but the compiler does not know about this. We *promise*
 ///             // that we always call `prepare_inputs`.
-///             std::hint::unreachable_unchecked()
+///             unsafe { std::hint::unreachable_unchecked() }
 ///         }
 ///         // The compiler would normally introduce a check here that prevents
 ///         // a division by zero. However, if `divisor` was zero, the branch

library/core/src/intrinsics/mod.rs

@@ -1703,12 +1703,12 @@ pub const fn forget<T: ?Sized>(_: T) {
 /// ```
 /// struct R<'a>(&'a i32);
 /// unsafe fn extend_lifetime<'b>(r: R<'b>) -> R<'static> {
-///     std::mem::transmute::<R<'b>, R<'static>>(r)
+///     unsafe { std::mem::transmute::<R<'b>, R<'static>>(r) }
 /// }
 ///
 /// unsafe fn shorten_invariant_lifetime<'b, 'c>(r: &'b mut R<'static>)
 ///                                              -> &'b mut R<'c> {
-///     std::mem::transmute::<&'b mut R<'static>, &'b mut R<'c>>(r)
+///     unsafe { std::mem::transmute::<&'b mut R<'static>, &'b mut R<'c>>(r) }
 /// }
 /// ```
 ///
@@ -4498,11 +4498,11 @@ pub const unsafe fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: us
 ///
 ///     // SAFETY: Our precondition ensures the source is aligned and valid,
 ///     // and `Vec::with_capacity` ensures that we have usable space to write them.
-///     ptr::copy(ptr, dst.as_mut_ptr(), elts);
+///     unsafe { ptr::copy(ptr, dst.as_mut_ptr(), elts); }
 ///
 ///     // SAFETY: We created it with this much capacity earlier,
 ///     // and the previous `copy` has initialized these elements.
-///     dst.set_len(elts);
+///     unsafe { dst.set_len(elts); }
 ///     dst
 /// }
 /// ```

library/core/src/mem/maybe_uninit.rs

@@ -98,7 +98,7 @@ use crate::{fmt, intrinsics, ptr, slice};
 ///
 /// unsafe fn make_vec(out: *mut Vec<i32>) {
 ///     // `write` does not drop the old contents, which is important.
-///     out.write(vec![1, 2, 3]);
+///     unsafe { out.write(vec![1, 2, 3]); }
 /// }
 ///
 /// let mut v = MaybeUninit::uninit();
@@ -844,7 +844,7 @@ impl<T> MaybeUninit<T> {
     /// # #![allow(unexpected_cfgs)]
     /// use std::mem::MaybeUninit;
     ///
-    /// # unsafe extern "C" fn initialize_buffer(buf: *mut [u8; 1024]) { *buf = [0; 1024] }
+    /// # unsafe extern "C" fn initialize_buffer(buf: *mut [u8; 1024]) { unsafe { *buf = [0; 1024] } }
     /// # #[cfg(FALSE)]
     /// extern "C" {
     ///     /// Initializes *all* the bytes of the input buffer.

library/core/src/mem/transmutability.rs

@@ -32,7 +32,7 @@ use crate::marker::{ConstParamTy_, UnsizedConstParamTy};
 ///         src: ManuallyDrop::new(src),
 ///     };
 ///
-///     let dst = transmute.dst;
+///     let dst = unsafe { transmute.dst };
 ///
 ///     ManuallyDrop::into_inner(dst)
 /// }

library/core/src/ptr/const_ptr.rs

@@ -724,13 +724,13 @@ impl<T: ?Sized> *const T {
     /// that their safety preconditions are met:
     /// ```rust
     /// # #![feature(ptr_sub_ptr)]
-    /// # unsafe fn blah(ptr: *const i32, origin: *const i32, count: usize) -> bool {
+    /// # unsafe fn blah(ptr: *const i32, origin: *const i32, count: usize) -> bool { unsafe {
     /// ptr.sub_ptr(origin) == count
     /// # &&
     /// origin.add(count) == ptr
     /// # &&
     /// ptr.sub(count) == origin
-    /// # }
+    /// # } }
     /// ```
     ///
     /// # Safety

library/core/src/ptr/mut_ptr.rs

@@ -896,13 +896,13 @@ impl<T: ?Sized> *mut T {
     /// that their safety preconditions are met:
     /// ```rust
     /// # #![feature(ptr_sub_ptr)]
-    /// # unsafe fn blah(ptr: *mut i32, origin: *mut i32, count: usize) -> bool {
+    /// # unsafe fn blah(ptr: *mut i32, origin: *mut i32, count: usize) -> bool { unsafe {
     /// ptr.sub_ptr(origin) == count
     /// # &&
     /// origin.add(count) == ptr
     /// # &&
     /// ptr.sub(count) == origin
-    /// # }
+    /// # } }
     /// ```
     ///
     /// # Safety

library/core/src/ptr/non_null.rs

@@ -857,13 +857,13 @@ impl<T: ?Sized> NonNull<T> {
     /// that their safety preconditions are met:
     /// ```rust
     /// # #![feature(ptr_sub_ptr)]
-    /// # unsafe fn blah(ptr: std::ptr::NonNull<u32>, origin: std::ptr::NonNull<u32>, count: usize) -> bool {
+    /// # unsafe fn blah(ptr: std::ptr::NonNull<u32>, origin: std::ptr::NonNull<u32>, count: usize) -> bool { unsafe {
     /// ptr.sub_ptr(origin) == count
     /// # &&
     /// origin.add(count) == ptr
     /// # &&
     /// ptr.sub(count) == origin
-    /// # }
+    /// # } }
     /// ```
     ///
     /// # Safety